Recovery system using fluid coupling on power generating system

ABSTRACT

A power generating system can recover exhaust heat from a working fluid of a fluid coupling and utilize the recovered exhaust heat to generate power. In the power generating system, water is supplied to a boiler by a feed pump to generate steam, a steam turbine is driven by using the generated steam to generate power, the steam discharged from the steam turbine is condensed in a condenser, and then the condensed water is resupplied to the boiler by the feed pump. The power generating system includes a fluid coupling provided between the feed pump and a motor to transmit a torque from the motor to the feed pump by a working fluid, and the condensed water supplied from the condenser is heated by the working fluid discharged from the fluid coupling.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a power generating system, and moreparticularly to a power generating system which can recover exhaust heatfrom a working fluid of a fluid coupling and utilize the recoveredexhaust heat to generate power.

2. Background Art

There has been known a fluid coupling in which an impeller is coupled toa drive shaft (input shaft) and a runner is coupled to a driven shaft(output shaft), and power is transmitted from a driving source to adriven source through a working oil which fills a casing. The fluidcoupling is employed to drive a feed pump or a blower at a variablespeed in a thermal power plant, a nuclear power plant or the like, andto drive a pump or a blower at a variable speed in an ironworks or thelike. When the pump or the blower is driven by the fluid coupling at avariable speed, a rotational speed of a load side, i.e. a drivenmachine, can be varied continuously from a minimum rotational speed to amaximum rotational speed by using a scoop tube. However, slip which is arotational speed difference between a prime mover and a driven machinecauses a slip loss.

When the rotational speed of the driven machine is low, the slip lossbecomes large. Therefore, in some cases, a power loss of the fluidcoupling reaches 14.8% of rated power of the driven machine at themaximum, resulting in a large energy loss.

A temperature of the working oil as a working fluid rises due to theslip loss of the fluid coupling. Therefore, the working oil dischargedfrom the fluid coupling has been returned to the fluid coupling afterbeing cooled down by an oil cooler. That is, heat caused by the sliploss in the fluid coupling is released outside through the oil cooler.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laid-Open Publication No. 8-135907

SUMMARY OF THE INVENTION

As described above, a temperature of the working oil as a working fluidrises due to the slip loss in the fluid coupling. However, the fluidcoupling has an oil cooler as an auxiliary machine so that the heatedworking oil discharged from the fluid coupling is cooled by the oilcooler and then returned to the fluid coupling. Therefore, heat of theslip loss generated in the fluid coupling is released outside withoutbeing recovered.

Inventors of the present invention have studied, from the viewpoint ofenergy saving, an entire system including a fluid coupling and a drivenmachine driven by the fluid coupling, and found the subject that heat ofthe slip loss in the fluid coupling which has been released outsideshould be recovered to promote energy saving in the entire system.

The present invention has been made in view of the above circumstances.It is therefore an object of the present invention to provide a powergenerating system which can recover heat of a slip loss in a fluidcoupling by recovering exhaust heat from a working fluid discharged fromthe fluid coupling and utilize the recovered exhaust heat (heat of theslip loss) to generate power.

In order to achieve the above object, according to a first aspect of thepresent invention, there is provided a power generating system in whichwater is supplied to a steam generator by a feed pump to generate steam,a steam turbine is driven by using the generated steam to generatepower, the steam discharged from the steam turbine is condensed in acondenser, and then the condensed water is resupplied to the steamgenerator by the feed pump; the power generating system comprising: afluid coupling provided between the feed pump and a driving machine fordriving the feed pump to transmit a torque from the driving machine tothe feed pump by a working fluid which fills an impeller chamber;wherein the condensed water supplied from the condenser is heated by theworking fluid discharged from the fluid coupling.

According to the first aspect of the present invention, water issupplied to a steam generator by a feed pump driven through a fluidcoupling by a driving machine to generate high-temperature steam in thesteam generator, and a steam turbine is driven by using thehigh-temperature steam to generate power. The steam discharged from thesteam turbine is supplied to a condenser where the steam is condensed,and the condensed water of the condenser is heated by a working fluiddischarged from the fluid coupling. The heated condensed water isresupplied to the steam generator. In this manner, heat of a slip lossin the fluid coupling can be recovered by means of heating the condensedwater by the working fluid discharged from the fluid coupling, and thusthermal efficiency of the entire steam turbine power generating systemcan be enhanced to improve power generation efficiency.

According to one aspect of the present invention, the power generatingsystem further comprises a heat exchanger for performing heat exchangebetween the working fluid discharged from the fluid coupling and thecondensed water supplied from the condenser to heat the condensed water.

According to one aspect of the present invention, the power generatingsystem further comprises a first heat exchanger for performing heatexchange between the working fluid discharged from the fluid couplingand a heat exchange medium; and a second heat exchanger for performingheat exchange between the heat exchange medium and the condensed watersupplied from the condenser; wherein the heat exchange medium is heatedby the heat exchange between the working fluid and the heat exchangemedium in the first heat exchanger, and the condensed water is heated bythe heat exchange between the heat exchange medium heated in the firstheat exchanger and the condensed water in the second heat exchanger.

According to this aspect of the present invention, because a circulationpath of the working fluid and a circulation path of the condensed waterare completely separated from each other, a risk of contamination of thecondensed water by the working fluid can be reduced.

According to one aspect of the present invention, the power generatingsystem further comprises a heat pump cycle which comprises anevaporator, a compressor, a refrigerant condenser and an expansionvalve; wherein the working fluid discharged from the fluid coupling issupplied to the evaporator to heat a refrigerant of said heat pumpcycle, and the condensed water is supplied from the condenser to therefrigerant condenser to heat the condensed water.

According to this aspect of the present invention, a refrigerant takesheat from the working fluid of the fluid coupling and evaporates in anevaporator to turn to a low-temperature and low-pressure gas, and thenthe low-temperature and low-pressure gas is compressed into ahigh-temperature and high-pressure gas by a compressor. Then, thehigh-temperature and high-pressure refrigerant gas releases heat by heatexchange with the condensed water in a refrigerant condenser to heat thecondensed water. At this time, the refrigerant is condensed andliquefied under high pressure. The resulting high-pressure liquidexpands through an expansion valve (pressure reducing valve) and isdepressurized to return to its original low-temperature and low-pressureliquid. Then, the low-temperature and low-pressure liquid is resuppliedto the evaporator. In this manner, a heat pump cycle which comprises aheat source of the working fluid discharged from the fluid coupling anda cooling source of the condensed water is constructed to heat thecondensed water by the working fluid, thereby enabling heat of a sliploss of the fluid coupling to be recovered. Therefore, thermalefficiency of the entire steam turbine power generating system can beenhanced to improve power generation efficiency.

According to one aspect of the present invention, the power generatingsystem further comprises a heat pump cycle which comprises anevaporator, a compressor, a refrigerant condenser and an expansionvalve; and a heat exchanger for performing heat exchange between thecondensed water supplied from the condenser and a heat exchange medium;wherein the working fluid discharged from the fluid coupling is suppliedto the evaporator to heat a refrigerant of said heat pump cycle, and theheat exchange medium is supplied to the refrigerant condenser to heatthe heat exchange medium; and the condensed water is heated in the heatexchanger by heat exchange between the heat exchange medium heated inthe refrigerant condenser and the condensed water supplied from thecondenser.

According to this aspect of the present invention, a refrigerant takesheat from the working fluid and evaporates in an evaporator to turn to alow-temperature and low-pressure gas, and then the low-temperature andlow-pressure gas is compressed into a high-temperature and high-pressuregas by a compressor. Then, the high-temperature and high-pressurerefrigerant gas releases heat by heat exchange with a heat exchangemedium supplied from a heat exchanger in a refrigerant condenser to heatthe heat exchange medium. At this time, the refrigerant gas is condensedand liquefied under high pressure. The resulting high-pressure liquidexpands through an expansion valve (pressure reducing valve) and isdepressurized to return to its original low-temperature and low-pressureliquid. Then, the low-temperature and low-pressure liquid is resuppliedto the evaporator. The heat exchange medium heated in the refrigerantcondenser returns to the heat exchanger where heat exchange is performedbetween the heat exchange medium and the condensed water supplied fromthe condenser to heat the condensed water. In this manner, a heat pumpcycle which comprises a heat source of the working fluid discharged fromthe fluid coupling and a cooling source of the condensed water isconstructed to heat the condensed water by the working fluid, therebyenabling heat of a slip loss of the fluid coupling to be recovered.Therefore, thermal efficiency of the entire steam turbine powergenerating system can be enhanced to improve power generationefficiency. Further, because a circulation path of the refrigerant inthe heat pump cycle and a circulation path of the condensed water arecompletely separated from each other, a risk of contamination of thecondensed water by the refrigerant can be reduced.

According to a second aspect of the present invention, there is provideda power generating system in which water is supplied to a steamgenerator by a feed pump to generate steam, a steam turbine is driven byusing the generated steam to generate power, the steam discharged fromthe steam turbine is condensed in a condenser, and then the condensedwater is resupplied to the steam generator by the feed pump; the powergenerating system comprising: a fluid coupling provided between the feedpump and a driving machine for driving the feed pump to transmit atorque from the driving machine to the feed pump by a working fluidwhich fills an impeller chamber; and a heat pump cycle which comprisesan evaporator, a compressor, a refrigerant condenser and an expansionvalve; wherein the working fluid discharged from the fluid coupling issupplied to the evaporator to heat a refrigerant of the heat pump cycle,part of the steam discharged from the steam turbine is supplied to therefrigerant condenser, and the steam discharged from the steam turbineis heated by the refrigerant which has been heated by the working fluiddischarged from the fluid coupling.

According to the second aspect of the present invention, water issupplied to a steam generator by a feed pump driven through a fluidcoupling by a driving machine to generate high-temperature steam in thesteam generator, and a steam turbine is driven by using thehigh-temperature steam to generate power. The steam discharged from thesteam turbine is supplied to a condenser where the steam is condensed.The working oil whose temperature has been raised is supplied to theevaporator in the heat pump cycle from the fluid coupling and part ofthe low-pressure steam discharged from the steam turbine is supplied tothe condenser. A refrigerant takes heat from the working oil of thefluid coupling and evaporates in the evaporator to turn to alow-temperature and low-pressure gas, and then the low-temperature andlow-pressure gas is compressed into a high-temperature and high-pressuregas by the compressor and supplied to the condenser. On the other hand,part of the low-pressure steam discharged from the steam turbine iscompressed by a compressor and supplied to a cooling side (a side to beheated) of the condenser. The high-temperature and high-pressurerefrigerant gas releases heat by heat exchange with the compressedlow-pressure steam in the condenser to heat the low-pressure steam,i.e., superheat the low-pressure steam. At this time, the refrigerant iscondensed and liquefied under high pressure. The resulting high-pressureliquid expands through the expansion valve (pressure reducing valve) andis depressurized to return to its original low-temperature andlow-pressure liquid. Then, the low-temperature and low-pressure liquidis resupplied to the evaporator. On the other hand, the steamsuperheated in the condenser is introduced into a middle stage of thesteam turbine and contributes to driving of the steam turbine.

According to one aspect of the present invention, the steam which hasbeen discharged from the steam turbine and heated in the condenser isintroduced into a middle stage of the steam turbine.

According to a third aspect of the present invention, there is provideda power generating system comprising: a fluid coupling provided betweena driving machine and a driven machine for transmitting a torque fromthe driving machine to the driven machine by a working fluid which fillsan impeller chamber; wherein the working fluid discharged from the fluidcoupling is supplied to a vapor generator, a refrigerant in the vaporgenerator is heated by the working fluid and is evaporated, a turbine isdriven by using the generated refrigerant vapor to generate power, therefrigerant vapor discharged from the turbine is introduced into arefrigerant condenser where the refrigerant vapor is cooled by a coolingmedium and condensed, and the condensed refrigerant liquid is resuppliedto the vapor generator.

According to the third aspect of the present invention, a working fluiddischarged from a fluid coupling is supplied to a vapor generator wherea refrigerant is heated by heat exchange with the working fluid, andpart of the refrigerant evaporates to turn to high-temperaturerefrigerant vapor. Then, the refrigerant vapor is introduced into aturbine and drives the turbine to generate power. The refrigerant vapordischarged from the turbine is introduced into a refrigerant condenserand cooled by a cooling medium, thus being condensed and liquefied. Theliquefied refrigerant is resupplied to the vapor generator. In thismanner, the refrigerant is evaporated by utilizing exhaust heat of theworking fluid of the fluid coupling, and the turbine is driven by usingthe refrigerant vapor to generate power, thereby enabling heat of a sliploss of the fluid coupling to be recovered. Therefore, thermalefficiency of the entire system for pumping a fluid such as a liquid ora gas by driving the driven machine using the fluid coupling can beenhanced to improve energy saving.

According to one aspect of the present invention, the refrigerantcomprises dichlorotrifluoroethane (HCFC123) or trifluoroethanol(CF₃CH₂OH).

According to the first aspect of the present invention, in the powergenerating system in which water is supplied to a steam generator by afeed pump to generate steam, a steam turbine is driven by using thegenerated steam to generate power, the steam discharged from the steamturbine is condensed in a condenser, and then the condensed water isresupplied to the steam generator by the feed pump, heat of a slip lossin the fluid coupling can be recovered by means of heating the condensedwater by the working fluid discharged from the fluid coupling fordriving the feed pump. Therefore, thermal efficiency of the entire powergenerating system can be enhanced to improve power generationefficiency. In some cases, a power loss of the fluid coupling reaches14.8% of rated power of the feed pump at the maximum. However, accordingto the present invention, most of the power loss can be recovered, andhence power generation efficiency of the entire power generating systemcan be enhanced tremendously.

According to the second aspect of the present invention, in the powergenerating system in which water is supplied to a steam generator by afeed pump to generate steam, a steam turbine is driven by using thegenerated steam to generate power, the steam discharged from the steamturbine is condensed in a condenser, and then the condensed water isresupplied to the steam generator by the feed pump, a heat pump cyclewhich comprises a heat source of a working oil discharged from the fluidcoupling for driving the feed pump and a cooling source of thelow-pressure steam discharged from the steam turbine is constructed toheat the low-pressure steam discharged from the steam turbine by theworking oil as a heat source, thereby recovering heat of a slip loss ofthe fluid coupling. Therefore, thermal efficiency of the entire steamturbine power generating system can be enhanced to improve powergeneration efficiency.

According to the third aspect of the present invention, the refrigerantis evaporated by utilizing exhaust heat of the working fluid of thefluid coupling and the turbine is driven by using the refrigerant vaporto generate power, thereby enabling heat of a slip loss in the fluidcoupling to be recovered. Therefore, thermal efficiency of the entiresystem for pumping a fluid such as a liquid or a gas by driving thedriven machine using the fluid coupling can be enhanced to improveenergy saving. In some cases, a power loss of the fluid coupling reaches14.8% of rated power of the driven machine at the maximum. However,according to the present invention, most of the power loss can berecovered as power in the exhaust heat power generating system, and thusthermal efficiency of the entire system can be enhanced remarkably usingthe fluid coupling.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a steam turbine power generatingsystem according to a first embodiment of a power generating system ofthe present invention.

FIG. 2 is a schematic view showing a schematic structure of a fluidcoupling.

FIG. 3 is a schematic view showing a steam turbine power generatingsystem according to a second embodiment of the present invention.

FIG. 4 is a schematic view showing a steam turbine power generatingsystem according to a third embodiment of the present invention.

FIG. 5 is a schematic view showing a modified example of the steamturbine power generating system shown in FIG. 4.

FIG. 6 is a schematic view showing another example of the powergenerating system according to the present invention.

FIG. 7 is a schematic view showing still another example of the powergenerating system according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A power generating system according to embodiments of the presentinvention will be described in detail with reference to FIGS. 1 through7. The same or corresponding structural members or elements are denotedby the same reference numerals in FIGS. 1 through 7 and will not bedescribed repetitively.

FIG. 1 schematically shows a steam turbine power generating systemaccording to a first embodiment of a power generating system of thepresent invention. In FIG. 1, a steam turbine power generating systemprovided in a thermal power plant is shown, and a boiler is used as asteam generator.

As shown in FIG. 1, in a steam turbine power generating system, water issupplied by a boiler feed pump BP to a boiler where high-temperaturesteam (high-pressure steam) is generated, and a steam turbine 2 isdriven by using the high-temperature steam and power is generated by apower generator 3 coupled to the steam turbine 2. Then, the steam(low-pressure steam) discharged from the steam turbine 2 is supplied toa condenser 4 where the steam is condensed, and the condensed water inthe condenser 4 is pumped up to a feed-water heater 5 by a condensatepump CP. Then, the condensed water heated in the feed-water heater 5 isresupplied to the boiler 1 by the boiler feed pump BP. The steam turbine2 has multistage blades and the blades at each stage are configured tocope with variable steam pressure optimally from the high-pressure steamimmediately after introduction to the steam turbine 2 to thelow-pressure steam immediately before discharge from the steam turbine2.

As shown in FIG. 1, in the steam turbine power generating system of thisembodiment, a fluid coupling 10 is provided between the boiler feed pumpBP and a motor M for driving the boiler feed pump BP so that a torque ofthe motor M is transmitted to the boiler feed pump BP through a workingoil (working fluid) of the fluid coupling 10.

FIG. 2 is a schematic view showing a schematic structure of the fluidcoupling 10. As shown in FIG. 2, the working oil which has flowed intoan impeller chamber is transferred to an outer circumferential side dueto a centrifugal force imparted by the impeller 11, and then flows intoa runner 12 to rotate the runner 12. A cylindrical oil layer is formeddue to the centrifugal force in a scoop tube chamber 13 and the workingoil is scooped through a forward end of the scoop tube 14. A rotationalspeed ratio of the impeller 11 to the runner 12 can be varied bychanging the position of the scoop tube 14 arbitrarily, therebycontrolling the rotational speed of the driven machine continuously. Inthe fluid coupling 10, slip which is a rotational speed differencebetween the impeller 11 and the runner 12 becomes a slip loss whichraises a temperature of the working oil.

Therefore, according to the embodiment shown in FIG. 1, a heat exchanger20 is provided to heat the condensed water by heat exchange between theworking oil of the fluid coupling 10 and the condensed water suppliedfrom the condenser 4. Specifically, the working oil discharged from thefluid coupling 10 through the scoop tube 14 is introduced via a workingoil path 21 into the heat exchanger 20 and the condensed water in thecondenser 4 is concurrently introduced into the heat exchanger 20 by thecondensate pump CP. Then, the heat exchange is performed between theworking oil and the condensed water to heat the condensed water in theheat exchanger 20. The working oil has a temperature of about 70° C. to90° C. at an inlet side of the heat exchanger 20. The working oil iscooled down to a temperature of about 50° C. by heat exchange in theheat exchanger 20, and is then returned to the fluid coupling 10. On theother hand, the condensed water has a temperature of about 30° C. to 35°C. at an inlet side of the heat exchanger 20. The condensed water isheated by heat exchange in the heat exchanger 20, and is then suppliedto the feed-water heater 5. Further, the condensed water which has beenheated in the feed-water heater 5 is resupplied to the boiler 1 by theboiler feed pump BP, as mentioned above.

According to the steam turbine power generating system of thisembodiment, heat of a slip loss of the fluid coupling 10 can berecovered by heating the condensed water by the working oil dischargedfrom the fluid coupling 10, and thus thermal efficiency of the entiresteam turbine power generating system can be enhanced to improve powergeneration efficiency. In some cases, a power loss of the fluid couplingreaches 14.8% of rated power of the boiler feed pump BP at the maximum.However, according to the present invention, most of the power loss canbe recovered in the heat exchanger 20, and hence power generationefficiency of the entire steam turbine power generating system can beremarkably enhanced.

FIG. 3 is a schematic view showing a steam turbine power generatingsystem according to a second embodiment of the present invention. In theembodiment shown in FIG. 3, there are provided a first heat exchanger 30which performs heat exchange between a working oil of a fluid coupling10 and a heat exchange medium, and a second heat exchanger 40 whichperforms heat exchange between the above heat exchange medium andcondensed water supplied from a condenser 4. Clean water is used as aheat exchange medium. Specifically, the working oil discharged from thefluid coupling 10 through the scoop tube 14 is introduced into the firstheat exchanger 30 through a working oil path 21 and the heat exchangemedium is introduced into the first heat exchanger 30 through a heatexchange medium path 31. Then, the heat exchange medium is heated byheat exchange between the working oil and the heat exchange medium. Acirculating pump 32 is provided in the heat exchange medium path 31. Theheat exchange medium which has been heated in the first heat exchanger30 is introduced into the second heat exchanger 40 through the heatexchange medium path 31 and the condensed water in the condenser 4 isintroduced into the second heat exchanger 40 by a condensate pump CP.Then, the condensed water is heated by heat exchange between the heatexchange medium and the condensed water.

The working oil discharged from the fluid coupling 10 has a temperatureof about 70° C. to 90° C. at an inlet side of the first heat exchanger30. The working oil is cooled down to a temperature of about 50° C. byheat exchange in the first heat exchanger 30, and is then returned tothe fluid coupling 10. On the other hand, the heat exchange medium isheated to a temperature close to the temperature of the working oil byheat exchange in the first heat exchanger 30, and is then supplied tothe second heat exchanger 40. Further, the condensed water has atemperature of about 30° C. to 35° C. at an inlet side of the secondheat exchanger 40. The condensed water is heated by heat exchange in thesecond heat exchanger 40, and is then supplied to the feed-water heater5. Then, the condensed water which has been heated in the feed-waterheater 5 is resupplied to the boiler 1 by the boiler feed pump BP, inthe same manner as the embodiment shown in FIG. 1.

According to a steam turbine power generating system of this embodiment,heat of a slip loss of the fluid coupling 10 can be recovered by heatingthe condensed water by the working oil discharged from the fluidcoupling 10, and thus thermal efficiency of the entire steam turbinepower generating system can be enhanced to improve power generationefficiency. In some cases, a power loss of the fluid coupling reaches14.8% of rated power of the boiler feed pump BP at the maximum. However,according to this embodiment, most of the power loss can be recovered inthe two heat exchangers 30 and 40, and hence power generation efficiencyof the entire steam turbine power generating system can be remarkablyenhanced.

In the embodiment shown in FIG. 3, because a circulation path of theworking oil and a circulation path of the condensed water are completelyseparated from each other, a risk of contamination of the condensedwater by the working oil can be reduced. Even if the heat exchangemedium path 31 is broken or damaged, the condensed water will not becontaminated because water which is as clean as the condensed water isused as a heat exchange medium which flows in the heat exchange mediumpath 31.

FIG. 4 is a schematic view showing a steam turbine power generatingsystem according to a third embodiment of the present invention. In theembodiment shown in FIG. 4, a heat pump cycle which comprises a heatsource of a working oil of a fluid coupling 10 and a cooling source ofcondensed water is constructed to heat the condensed water by theworking oil. Specifically, the heat pump cycle HP comprises anevaporator E, a compressor Comp, a condenser C serving as a refrigerantcondenser, and an expansion valve (pressure reducing valve) V. In theheat pump cycle HP, the working oil whose temperature has been raised issupplied to the evaporator E from the fluid coupling 10 and thecondensed water of the condenser 4 is supplied to the condenser C.Alternative for chlorofluorocarbon or the like is used as a refrigerantin the heat pump cycle HP.

In the steam turbine power generating system having the heat pump cycleHP shown in FIG. 4, a refrigerant takes heat from the working oil of thefluid coupling 10 and evaporates in the evaporator E to turn to alow-temperature and low-pressure gas, and then the low-temperature andlow-pressure gas is compressed into a high-temperature and high-pressuregas by a compressor Comp. Then, the high-temperature and high-pressurerefrigerant gas releases heat by heat exchange with the condensed waterin the condenser C to heat the condensed water. At this time, therefrigerant is condensed and liquefied under high pressure. Theresulting high-pressure liquid expands through the expansion valve(pressure reducing valve) V and is depressurized to return to itsoriginal low-temperature and low-pressure liquid. Then, thelow-temperature and low-pressure liquid is resupplied to the evaporatorE.

The working oil discharged from the fluid coupling 10 has a temperatureof about 70° C. to 90° C. at an inlet side of the evaporator E. Theworking oil is cooled down to a temperature of about 50° C. by removalof heat in the evaporator E, and is then returned to the fluid coupling10. On the other hand, the condensed water has a temperature of about30° C. to 35° C. at an inlet side of the condenser C. The condensedwater is heated by heat exchange in the condenser C, and is thensupplied to the feed-water heater 5. Further, the condensed water whichhas been heated in the feed-water heater 5 is resupplied to the boiler 1by the boiler feed pump BP, in the same manner as the embodiment shownin FIG. 1.

According to the steam turbine power generating system of thisembodiment, a heat pump cycle HP which comprises a heat source of aworking oil discharged from a fluid coupling 10 and a cooling source ofcondensed water is constructed to heat the condensed water by theworking oil, and thus heat of a slip loss of the fluid coupling 10 canbe recovered. Therefore, thermal efficiency of the entire steam turbinepower generating system can be enhanced to improve power generationefficiency. In some cases, a power loss of the fluid coupling reaches14.8% of rated power of the boiler feed pump BP at the maximum. However,according to the present invention, most of the power loss can berecovered by utilizing the heat pump cycle HP, and thus power generationefficiency of the entire steam turbine power generating system can beremarkably enhanced.

FIG. 5 is a schematic view showing a modified example of a steam turbinepower generating system shown in FIG. 4. In the embodiment shown in FIG.4, the condensed water is directly heated in the condenser C in the heatpump cycle HP. However, in the embodiment shown in FIG. 5, a heatexchanger 50 is provided to perform heat exchange between condensedwater supplied from a condenser 4 and a heat exchange medium, and theheat exchange medium supplied from the heat exchanger 50 is heated in acondenser C serving as a refrigerant condenser in a heat pump cycle HP.The heat exchange medium circulates between the condenser C and the heatexchanger 50 by a heat exchange medium path 51 and a circulating pump 52provided in the heat exchange medium path 51. Clean water is used as aheat exchange medium. Specifically, a refrigerant takes heat from theworking oil and evaporates in the evaporator E to turn to alow-temperature and low-pressure gas, and then the low-temperature andlow-pressure gas is compressed into a high-temperature and high-pressuregas by a compressor Comp. Then, the high-temperature and high-pressurerefrigerant gas releases heat by heat exchange with the heat exchangemedium supplied from the heat exchanger 50 through the heat exchangemedium path 51 in the condenser C to heat the heat exchange medium. Atthis time, the refrigerant is condensed and liquefied under highpressure. The resulting high-pressure liquid expands through theexpansion valve (pressure reducing valve) V and is depressurized toreturn to its original low-temperature and low-pressure liquid. Then,the low-temperature and low-pressure liquid is resupplied to theevaporator E. The heat exchange medium which has been heated in thecondenser C returns to the heat exchanger 50 where the heat exchangemedium performs heat exchange with the condensed water supplied from thecondenser 4 to heat the condensed water.

In the embodiment shown in FIG. 5, because a circulation path of therefrigerant in the heat pump cycle HP and a circulation path of thecondensed water are completely separated from each other, a risk ofcontamination of the condensed water by the refrigerant can be reduced.Even if the heat exchange medium path 51 is broken or damaged, thecondensed water will not be contaminated because water which is as cleanas the condensed water is used as a heat exchange medium which flows inthe heat exchange medium path 51.

The working oil discharged from the fluid coupling 10 has a temperatureof about 70° C. to 90° C. at an inlet side of the evaporator E. Theworking oil is cooled down to a temperature of about 50° C. by removalof heat in the evaporator E. On the other hand, the condensed water hasa temperature of about 30° C. to 35° C. at an inlet side of the heatexchanger 50. The condensed water is heated by heat exchange in the heatexchanger 50, and is then supplied to the feed-water heater 5. Further,the condensed water which has been heated in the feed-water heater 5 isresupplied to the boiler 1 by the boiler feed pump BP, in the samemanner as the embodiment shown in FIG. 1.

According to the steam turbine power generating system of thisembodiment, a heat pump cycle HP which comprises a heat source of aworking oil discharged from a fluid coupling 10 and a cooling source ofcondensed water is constructed to heat the condensed water by theworking oil, and thus heat of a slip loss of the fluid coupling 10 canbe recovered. Therefore, thermal efficiency of the entire steam turbinepower generating system can be enhanced to improve power generationefficiency.

FIG. 6 is a schematic view showing another embodiment of a powergenerating system according to the present invention. While the steamturbine power generating system shown in FIGS. 1 through 5 is configuredto recover heat of a slip loss of the fluid coupling 10 by heating thecondensed water as a heat source of a working oil discharged from thefluid coupling 10, the power generating system according to theembodiment shown in FIG. 6 is different in that heat of a slip loss ofthe fluid coupling 10 is recovered by heating low-pressure steamdischarged from the steam turbine 2 as a heat source of a working oildischarged from the fluid coupling 10 and by introducing the heatedlow-pressure steam into a low-pressure stage of the steam turbine 2.Further, in the embodiment shown in FIG. 6, in order to obtain hightemperature which is enough to heat the low-pressure steam, a heat pumpcycle is used in the same manner as the embodiment shown in FIG. 4, andthe heat pump cycle which comprises a heat source of a working oildischarged from the fluid coupling 10 and a cooling source of thelow-pressure steam discharged from the steam turbine is constructed.Specifically, the heat pump cycle HP comprises an evaporator E, acompressor Comp, a condenser C, and an expansion valve (pressurereducing valve) V. In the heat pump cycle HP, the working oil whosetemperature has been raised is supplied to the evaporator E from thefluid coupling 10 and part of the low-pressure steam discharged from thesteam turbine 2 is supplied to the condenser C. Alternative forchlorofluorocarbon or the like is used as a refrigerant in the heat pumpcycle HP.

In the steam turbine power generating system having the heat pump cycleHP shown in FIG. 6, a refrigerant takes heat from the working oil of thefluid coupling 10 and evaporates in the evaporator E to turn to alow-temperature and low-pressure gas, and then the low-temperature andlow-pressure gas is compressed into a high-temperature and high-pressuregas by the compressor Comp and supplied to the condenser C. On the otherhand, part of the low-pressure steam discharged from the steam turbine 2is compressed by a compressor Comp2 and supplied to a cooling side (aside to be heated) of the condenser C. The high-temperature andhigh-pressure refrigerant gas releases heat by heat exchange with thecompressed low-pressure steam in the condenser C to heat thelow-pressure steam, i.e., superheat the low-pressure steam. At thistime, the refrigerant is condensed and liquefied under high pressure.The resulting high-pressure liquid expands through the expansion valve(pressure reducing valve) V and is depressurized to return to itsoriginal low-temperature and low-pressure liquid. Then, thelow-temperature and low-pressure liquid is resupplied to the evaporatorE. On the other hand, the steam superheated in the condenser C isintroduced into a middle stage of the steam turbine 2 and contributes todriving of the steam turbine 2.

The working oil discharged from the fluid coupling 10 has a temperatureof about 70° C. to 90° C. at an inlet side of the evaporator E. Theworking oil is cooled down to a temperature of about 50° C. by removalof heat in the evaporator E, and is then returned to the fluid coupling10. On the other hand, the low-pressure steam is superheated by heatexchange in the condenser C, and is then supplied to the middle stage ofthe steam turbine 2. The low-pressure steam whose temperature hasdecreased by driving the steam turbine 2 is partly compressed by thecompressor Comp2 again and supplied to the condenser C, and the rest ofthe low-pressure steam is returned to the condenser 4 where the steam iscondensed.

The steam superheated in the condenser C may be introduced not into themiddle stage of the steam turbine 2 but into a second steam turbineprovided separately from the steam turbine 2, and the second steamturbine may be configured to recover power. Also in this case, the steamafter recovery of power is returned to the condenser 4 where the steamis condensed.

According to the steam turbine power generating system of thisembodiment, a heat pump cycle HP which comprises a heat source of aworking oil discharged from the fluid coupling 10 and a cooling sourceof the low-pressure steam discharged from the steam turbine 2 isconstructed to heat the low-pressure steam discharged from the steamturbine 2 by the working oil as a heat source, thereby recovering heatof a slip loss of the fluid coupling 10. Therefore, thermal efficiencyof the entire steam turbine power generating system can be enhanced toimprove power generation efficiency. In some cases, a power loss of thefluid coupling reaches 14.8% of rated power of the boiler feed pump BPat the maximum. However, according to the present invention, most of thepower loss can be recovered by utilizing the heat pump cycle HP, andthus power generation efficiency of the entire steam turbine powergenerating system can be remarkably enhanced.

In the steam turbine power generating system shown in FIGS. 1 through 6,the steam turbine power generating system provided in the thermal powerplant has been explained. In the case of a nuclear power plant, althougha boiler will be replaced with a steam generator, the structure torecover heat from the working oil of the fluid coupling is the same asthat of the thermal power plant.

FIG. 7 is a schematic view showing still another embodiment of a powergenerating system according to the present invention. In the embodimentshown in FIG. 7, the power generating system is an exhaust heat powergenerating system which comprises a heat source of a working oil of afluid coupling 10 and a cooling source of cooling water to generatepower. In the exhaust heat power generating system, a refrigerant isevaporated by exhaust heat from the working oil of the fluid coupling,and a turbine is driven by using refrigerant vapor to generate power. Asa refrigerant, a low-boiling refrigerant whose boiling point is around40° C., for example, dichlorotrifluoroethane (HCFC123) ortrifluoroethanol (CF₃CH₂OH) is used.

As shown in FIG. 7, a fluid coupling 10 is provided between a drivingmachine 60 and a driven machine 61. The driving machine 60 comprises amotor or an engine, and the driven machine 61 comprises an air blower ora pump. A fluid coupling 10 has the same structure as that shown in FIG.2. A working oil discharged from the fluid coupling 10 is supplied to avapor generator 63. A refrigerant in the vapor generator 63 is heated byheat exchange with the working oil. Therefore, part of the refrigerantevaporates to turn to high-temperature refrigerant vapor. Then, therefrigerant vapor is introduced into a turbine 64 and drives the turbine64 to generate power by a power generator 65 coupled to the turbine 64.The refrigerant vapor discharged from the turbine 64 is introduced intoa condenser 66 and cooled by cooling water, thus being condensed andliquefied. The liquefied refrigerant is resupplied to the vaporgenerator 63 by a refrigerant pump 67. The working oil discharged fromthe fluid coupling 10 has a temperature of about 70° C. to 90° C. at aninlet side of the vapor generator 63. The working oil is cooled down toa temperature of about 50° C. by removal of heat in the vapor generator63, and then returns to the fluid coupling 10.

According to the exhaust heat power generating system shown in FIG. 7,heat of a slip loss of the fluid coupling 10 can be recovered byutilizing exhaust heat from the working oil of the fluid coupling 10 toevaporate the refrigerant and by using refrigerant vapor to drive theturbine 64, thereby generating power. Therefore, thermal efficiency ofthe entire system for pumping a fluid such as a liquid or a gas bydriving the driven machine 61 using the fluid coupling 10 can beenhanced to achieve energy saving. In some cases, a power loss of thefluid coupling reaches 14.8% of rated power of the driven machine 61 atthe maximum. However, according to this embodiment, most of the powerloss can be recovered as power in the exhaust heat power generatingsystem, and hence thermal efficiency of the entire system can beremarkably enhanced.

In the embodiment shown in FIG. 7, the air blower or the pump is used asthe driven machine 61, however, a rotary machine such as a blower or acompressor may be used as the driven machine 61. According to thisembodiment, thermal efficiency of the entire system having these rotarymachines can be improved.

Although preferred embodiments of the present invention have been shownand described in detail, it should be understood that various changesand modifications may be made therein without departing from the scopeof the appended claims.

For example, in the above embodiments, the temperature of the workingoil whose heat is recovered is about 70° C. to 90° C. However, thetemperature of the working oil can be lower or higher than thetemperature of about 70° C. to 90° C. by controlling the circulatingflow rate of the working oil. The temperature of the working oil may beraised to 100° C. or higher. The higher the temperature of the workingoil is, the higher the efficiencies of heat exchange for the condensedwater, the heat exchange medium and the refrigerant are.

The present invention can be applied to a power generating system whichcan recover exhaust heat from a working fluid of a fluid coupling andutilize the recovered exhaust heat to generate power.

REFERENCE SIGNS LIST

-   1 boiler-   2 steam turbine-   3 power generator-   4 condenser-   5 feed-water heater-   10 fluid coupling-   11 impeller-   12 runner-   13 scoop tube chamber-   14 scoop tube-   20, 50 heat exchanger-   21 working oil path-   30 first heat exchanger-   31, 51 heat exchange medium path-   32, 52 circulating pump-   40 second heat exchanger-   60 driving machine-   61 driven machine-   63 vapor generator-   64 turbine-   65 power generator-   66 condenser-   67 refrigerant pump-   C condenser-   Comp compressor-   E evaporator-   V expansion valve (pressure reducing valve)-   M motor-   BP boiler feed pump-   CP condensate pump-   HP heat pump cycle

1. A power generating system comprising: a fluid coupling providedbetween a driving machine and a driven machine for transmitting a torquefrom the driving machine to the driven machine by a working oil whichfills an impeller chamber of said fluid coupling; wherein the workingoil has a temperature of 70° C. to 90° C., is discharged from said fluidcoupling and is supplied to a vapor generator, a refrigerant in saidvapor generator is heated by the working oil and is evaporated to form arefrigerant vapor, a turbine is driven by using the refrigerant vapor togenerate power, the refrigerant vapor is discharged from said turbineand is introduced into a refrigerant condenser where the refrigerantvapor is cooled by a cooling medium and condensed to form a refrigerantliquid, and the refrigerant liquid is resupplied to said vaporgenerator.
 2. The power generating system according to claim 1, whereinsaid refrigerant comprises dichlorotrifluoroethane (HCFC123) ortrifluoroethanol (CF₃CH₂OH).